Cutting of glass

ABSTRACT

Cutter heads in a glass-cutting machine are actuated, using a constant-reluctance motor means. Score lines of predetermined depth are obtained, despite small variations in the thickness of the glass, and without use of a pneumatic system that is slowacting and difficult to maintain. The pressure exerted by the cutter head responds rapidly to changes in the d-c potential supplied to the motor means, making it possible to vary the depth of the score as desired during the making of a pattern cut, which could not be done with the pneumatic or spring-loaded means of the prior art.

United tes atent 1191 Bier et al. Sept. 4, 1973 CUTTING 0F GLASS3,439,849 4/1969 Matsuzaki et al 225/965 3,474,944 10/1969 Chatelain atal 225 2 [75] lnvenmrs- Dav! Meadmvlands, 3,58l,6l5 6/1971 Kaneshige etal 83/6 x Edward W. Curtze, Pittsburgh, both of Pa.

Assignee: PPG Industries, Inc., Pittsburgh, Pa.

Filed: June 23, 1972 Appl. No.: 265,923

Related U.S. Application Data Continuation of Ser. No. 68,305, Aug. 31,1970, abandoned.

U.S. Cl 83/8, 83/12, 225/2, 225/96 Int. Cl B266 3/08 Field of Search83/6, 8, 12, 487, 83/488, 489, 428; 225/2, 96, 96.5

References Cited UNITED STATES PATENTS ll/l966 Sasabuchi et al. 83/12 XPrimary ExaminerFrank T. Yost Attorney-Thomas F. Shanahan [5 7] ABSTRACTCutter heads in a glass-cutting machine are actuated, using aconstant-reluctance motor means. Score lines of predetermined depth areobtained, despite small variations in the thickness of the glass, andwithout use of a pneumatic system that is slow-acting and difficult tomaintain. The pressure exerted by the cutter head responds rapidly tochanges in the d-c potential supplied to the motor means, making itpossible to vary the depth of the score as desired during the making ofa pattern cut, which could not be done with the pneumatic orspring-loaded means of the prior art.

10 Claims, 5 Drawing Figures ADJUSTABLE n-c Powee sou/aceCONSTANT-RELUCTANCE MOTOR MEANS Patented Sept. 4, 1973 3,756,104

2- ADJUSTABLE n-c POWER sourzcs CONSTANT-RELUCTANCE MOTOR. MEANS FIG. 4

k DA W0 A, 511% 66 0 wmw w. cueTze IG. BY F 5 WMMM ATTORNEY CUTTING OFGLASS This is a continuation of application Ser. No. 68,305, filed Aug.31, 1970, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to the cutting of glass.

2. Description of the Prior Art Various equipment is known for thecutting of glass, such as U. S. Pat. Nos. 3,107,834; 3,146,926;3,151,794; and 3,253,756. In none of the foregoing is there used theconcept of actuating a cutter head by means of a motor that exerts uponthe glass being cut a force that remains substantially constant or isvaried at will in a desired and predetermined manner because of the useof a constant-reluctance motor means. Instead, as has been usual in theart of cutting glass, the cutter head is urged against the glass eitherby springloaded means or by means of a pneumatic cylinder. Bothspring-loaded means and pneumatic-cylinder means have substantialdrawbacks. Spring-loaded means are not capable of being adjusted readilywhile a cut is in progress, e.g., in the cutting of a shape such as awindshield blank, so as to exert greater or lesser pressure and generatea score of greater or lesser depth, respectively, in the vicinity of acorner. Pneumatic means have the drawbacks that they are costly toinstall and maintain and that they are relatively slowacting, so that itis not ordinarily possible with such pneumatic means to change, asdesired, the intended depth of the score.

The concept of electrically or electromagnetically actuating a cutterhead that is used in the cutting of glass is not novel. It is known, forexample, from Drake U. S. Pat. No. 1,856,128 or lnsolio U. S. Pat. No.3,276,302, to use for the cutting of glass a cutter head that isactuated electromagnetically. The problem, however, with the devices ofthe prior art has been that it is difficult to control the amount offorce exerted by the cutter head upon the glass. It is by no meansunusual for the thickness of the glass being cut to vary by a fewthousandths of an inch, yet even such relatively small variations, inthe cutting of pieces of glass having a thickness between 2 andmillimeters, is likely to lead to considerable variations in the depthof the score. There has been, of course, the possibility of using in thevicinity of the cutter wheel a reference wheel that is intended to rideupon the upper surface of the glass being scored, but it has ordinarilybeen impossible to arrange for any variation in the spacing between suchreference wheel and the cutter wheel while a cut is in progress, sincemeans sufficiently fast-acting to permit such adjustment to be made inthe depth of the score being produced has been unknown, prior to theinstant invention.

It may be considered that direct-current torque motors are, per se,already known. Such devices comprise a rotor of permanent-magnetmaterial of high penneability, suitably keyed to a shaft. In operativeassociation with the rotor of permanent-magnet material, there areprovided a plurality of coils actuated by a variable-magnitudedirect-current source, such that when current is fed to the coils, thereis a tendency for the above-mentioned rotor to assume a home position,and such that whenever the above-mentioned rotor is away from said homeposition, there is exerted upon the above-mentioned shaft a torqueproportional to the magnitude of the direct-current potential providedto the above-mentioned. coils.

SUMMARY OF THE INVENTION Cutter heads in a glass-cutting machine areactuated, using a constant-reluctance motor means. Score lines ofpredetermined depth are obtained, despite small variations in thethickness of the glass, and without use of a pneumatic system that isslow-acting and difficult to maintain. The pressure exerted by thecutter head responds rapidly to changes in the d-c potential supplied tothe motor means, making it possible to vary the depth of the score asdesired during the making of a pattern cut, which could not be done withthe pneumatic or spring-loaded means of prior art.

DESCRIPTION OF THE DRAWINGS A complete understanding of the inventionmay be had from the foregoing and following description thereof, takentogether with the appended drawings, in which:

FIG. 1 is a schematic diagram, indicating the invention in its broadestaspect;

FIG. 2 is a detailed view, indicating one particular constant-reluctancemotor means for use in the invention as described in FIG. 1;

FIG. 3 comprises a block diagram of an embodiment of the invention;

FIG. 4 represents the outline of a light of a vehicle; and

FIG. 5 is a graph indicating variations in the voltage applied to aconstant-reluctance motor means in accordance with the invention in thescoring of a sheet of glass to produce the light of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I, there isindicated in block 2 an adjustable direct-current power source, such asa combination of battery and rheostat.

As indicated at 4, such a power source is connected to aconstant-reluctance motor means 6. Preferably, but not necessarily, theconstant-reluctance motor means 6 comprises a direct-current torquemotor of the general kind indicated in FIG. 2.

Referring to FIG. 2, a direct-current torque motor, indicated generallyas 8, may be considered as comprising a pair of coils 10, 12 containedwithin a suitable housing 14. Direct electrical current is fed from asource 16 through a rheostat 18, the output lines 20, 22 of which areconnected to the taps 24, 26 of the coils l0, 12. The passage of directcurrent through the coils 10, 12 generate within the motor 8 a suitableelectrical field, tending to influencethe location of the rotor 28,which is made of permanent-magnet material such as an Alnico alloy ofhigh energy product and has, as indicated, a north pole 30 and a southpole 32. The rotor 28 has centrally thereof an opening 34 containing asleast one keyway 36. When the rotor 28 is in the position indicated indash-dot lines in FIG. 2, and directcurrent electrical power is suppliedthrough the taps 24, 26, there is exerted upon the rotor 28 a suitableforce that tends to turn the rotor 28 to the position indicated in solidlines in FIG. 2.

Those skilled in the art will understand how it is possible to positionwithin the opening 34 a keyed shaft 38, providing the shaft 38 withsuitable bearings in the vicinity of its ends and associatingoperatively with the shaft 38 a fork or yoke (not shown) that cooperateswith a suitable key of the shaft 38 and exerts, as necessary, a forceupon a cutter head 40.

Referring to FIG. 1, there is indicated at 42 an operative connectionbetween the constant-reluctance motor means 6 and the cutter head 40,and this connection may be of the kind indicated above, or it may be ofa different kind, such as will suggest itself to a person of ordinaryskill in the art.

Cutter head 40 comprises a cutter wheel 44, which may, for example, bemade of sintered tungsten carbide or other wear-resistant and hardmaterial, possibly having some diameter such as millimeters or less anda cutter angle such as about 140 or less, with the wheel 44 beingjournaled for rotation about an axis or shaft indicated at 46. The wheel44 comes into contact with a sheet of glass G to be cut or scored withthe glass G being supported on a plurality of rollers 48, suitablydriven by suitable means (not shown).

Referring now to FIG. 3, there is indicated a combi nation of equipmentparticularly suited for the cutting of a shaped or patterned piece ofglass, such as that shown in FIG. 4. The apparatus shown in FIG. 3comprises a function generator 50, connected as indicated at 52 to anull-balance potentiometer 54, which is connected as indicated at 56 toa constant-reluctance motor means 58, which may be of the general kindindicated above. The constant-reluctance motor means as indicated isconnected operatively at 60 to a cutter head 62 used, as was the cutterhead 40, for the scoring of a piece of glass. In the cutting of a blankfor a windshield, sidelight or backlight, possibly having a shape suchas that indicated in FIG. 4, there is produced by the function generator50 a direct-current potential such as that indicated by the line 66 inFIG. 5. In FIG. 5, line 68 indicates a basis or zero potential. Thepiece 64 as shown in FIG. 4 may be cut or broken from a larger piece ofglass containing the same, and quite appropriately, if the cutter head62 is so operated as to start, for example, at the location indicated at70 in FIG. 4, and the corner indicated in 72 is then cut with therebeing used an appropriately increased pressure by the cutter head 62upon the glass, such as may be produced by the increase in the signal onthe line 52 indicated by the hump at 74 in the line 66. Then, as thecutter head traverses the portion 75 of the piece 64, the functiongenerator 50 produces the portion 76 of the line 66, with the pressureexerted by the cutter head 62 upon the glass being increased as theportion in the vicinity of corner 78 is being cut, as is indicated bythe hump 80 in the line 66. Similarly, the humps 82 and 84 correspond tothe comers 86 and 88 of the piece 64.

Those skilled in the art will understand that, in most instances, it isessential that the force exerted by the cutter head upon the glass be onthe order of 10 pounds or more, and preferably about pounds or more, inorder that a score of suitable depth may be obtained. If the wheelcontained in the cutter head is somewhat sharper, it will in someinstances be possible to use a lesser pressure. On the other hand, it isdesirable not to use a pressure so great as to cause immediatefracturing of the glass being out throughout its thickness.

For the most part, it is desirable that the score be made (except whenthe cross-cutting of a glass ribbon, complete with edge portions and/oredge bulbs, is being practiced) to be located at a suitable distancewith respect to the edge of the piece being scored for cutting, such asa minimum of six or eight times the thickness of the glass.

The invention is of especial usefulness in connection with the cuttingof a large sheet or ribbon of glass into a plurality of segments bymeans ofa plurality of cutter heads located upon a cutter bar. Inaccordance with prior-art practices, it has hitherto been considerednecessary either to use a pneumatic system, with its attendant dangersof the kinking or the wearing of the cords or lines connecting thepneumatic supply source to the cutter heads, or to use a spring-loadedapparatus, with its attendant difficulty that it is inconvenient toadjust the spring means associated with each of the cutter heads so thata score line of adequate and desired depth is obtained.

Although the invention has been described in connection with adirect-current torque motor, it will be apparent to those skilled in theart that other suitable constant-reluctance motor means may be devisedand used. What is required is that there be provided an electrical ormagnetic means that operates on the basis of a substantially constantair gap and a substantially constant environment of magneticpermeability. This is to be distinguished from the use of anelectromagnet or solenoid, where the air gap goes from a substantialvalue such as 3 millimeters or more to substantially zero, possibly withoccasional excursions thereafter of up to l or 2 millimeters. With theuse of such equipment, it is substantially impossible to exert aconstant force, as is contemplated in accordance with the principles ofthe instant invention.

Those skilled in the art of cutting glass will appreciate from theforegoing disclosure that remarkable novel effects can be obtained if aseries of sheets or a moving ribbon is cut by means of sets of cuttersof the kind taught above that operate, one set transversely of the glassin its travel and one set longitudinally, with the positioning of thecutter heads being automatically controlled and with the cutter headsbeing raised or lowered at precisely chosen moments. The actuation is soquick and precise that it becomes possible to envision usinginterrupted-cut practices that were hitherto impractical. The losses, inchanging from one pattern of cutting to another, are much reduced. Withthe faster and more reliable action obtained with the present invention,it is possible to cut more closely around a defect, so that less glassis discarded. The cutting of flat glass to meet a customers sizespecifications may be accomplished substantially more efficiently,rapidly and conveniently when the instant invention is practiced.

We claim as our invention:

1. An apparatus for cutting glass comprising, in combination, anadjustable source of current,

a constant-reluctance motor means operatively connected to said sourceof current, and

cutter-head means comprising a cutter wheel for scoring said glassoperatively connected to said constant-reluctance motor means to movesaid cutter wheel in a direction that intersects a major surface of saidglass.

2. Apparatus as defined in claim 1, characterized in that saidconstant-reluctance motor means is operatively connected to anadjustable source of direct current.

3. Apparatus as defined in claim 2, characterized in that saidconstant-reluctance motor means comprises a direct-current torque motor.

4. Apparatus as defined in claim 1, said apparatus being furthercharacterized in that said current source comprises a function generatorand a null-balance potentiometer operatively connected therewith.

5. Apparatus for cutting glass comprising, in combination, a motor meansincluding a movable member therein,

means for moving said member solely within the constant-reluctance rangeof said motor, and

cutter-head means comprising a cutter wheel for scoring said glassoperatively connected to said constant-reluctance motor means to movesaid cutter wheel in a direction that intersects a major surface of saidglass.

6. Apparatus as defined in claim 5, said apparatus being furthercharacterized in that said motor means comprises a direct-current torquemotor.

7. Apparatus as defined in claim 5, said apparatus being furthercharacterized in that said means for moving said member comprises afunction generator and a null-balance potentiometer operativelyconnected therewith.

8. A method of producing a score line upon a sheet of glass, said scoreline being of predetermined depth at predetermined locations along theextent of said score line, said method comprising the step of activatinga substantially constant-reluctance motor means that is operativelyassociated with a cutter wheel means to move said cutter wheel means ina direction that intersects a major surface of said glass.

9. A method as defined in claim 8, said method being furthercharacterized in that said score line forms a closed loop, saidsubstantially constant-reluctance motor means being operated so as toproduce in portions thereof corresponding to the comers of said loop ascore having a greater depth than said score exhibits in the remainingportions of said loop.

10. A method as defined in claim 8, characterized in that saidsubstantially constant-reluctance motor means comprises a direct-currenttorque motor.

1. An apparatus for cutting glass comprising, in combination, anadjustable source of current, a constant-reluctance motor meansoperatively connected to said source of current, and cutter-head meanscomprising a cutter wheel for scoring said glass operatively connectedto said constant-reluctance motor means to move said cutter wheel in adirection that intersects a major surface of said glass.
 2. Apparatus asdefined in claim 1, characterized in that said constant-reluctance motormeans is operatively connected to an adjustable source of directcurrent.
 3. Apparatus as defined in claim 2, characterized in that saidconstant-reluctance motor means comprises a direct-current torque motor.4. Apparatus as defined in claim 1, said apparatus being furthercharacterized in that said current source comprises a function generatorand a null-balance potentiometer operatively connected therewith. 5.Apparatus for cutting glass comprising, in combination, a motor meansincluding a movable member therein, means for moving said member solelywithin the constant-reluctance range of said motor, and cutter-headmeans comprising a cutter wheel for scoring said glass operativelyconnected to said constant-reluctance motor means to move said cutterwheel in a direction that intersects a major surface of said glass. 6.Apparatus as defined in claim 5, said apparatus being furthercharacterized in that said motor means comprises a direct-current torquemotor.
 7. Apparatus as defined in claim 5, said apparatus being furthercharacterized in that said means for moving said member comprises afunction generator and a null-balance potentiometer operativelyconnected therewith.
 8. A method of producing a score line upon a sheetof glass, said score line being of predetermined depth at predeterminedlocations along the extent of said score line, said method comprisingthe step of activating a substantially constant-reluctance motor meansthat is operatively associated with a cutter wheel means to move saidcutter wheel means in a direction that intersects a major surface ofsaid glass.
 9. A method as defined in claim 8, said method being furthercharacterized in that said score line forms a closed loop, saidsubstantially constant-reluctance motor means being operated so as toproduce in portions thereof corresponding to the corners of said loop ascore having a greater depth than said score exhibits in the remainingportions of said loop.
 10. A method as defined in claim 8, characterizedin that said substantially constant-reluctance motor means comprises adirect-current torque motor.